Just put one down, make sure their not twisted (unless you like the look of them being twisted, but be consistent), and pick up the new color and start knitting with it. Leave enough slack on it so that it's not scrunching up the knitting by connecting tightly from the row below.
Hope that helps.
KnittingHelp Queen Bee
"There is a vitality, a life force, an energy, a quickening that is translated through you into action, and because there is only one of you in all of time, this expression is unique. And if you block it, it will never exist through any other medium and it will be lost. The world will not have it. It is not your business to determine how good it is nor how valuable nor how it compares with other expressions. It is your business to keep it yours clearly and directly, to keep the channel open. You do not even have to believe in yourself or your work. You have to keep yourself open and aware to the urges that motivate you. Keep the channel open."
— Martha Graham